The present invention relates generally to the field of magnetic data storage and retrieval systems. In particular, the present invention relates a magnetic read head for use in a magnetic data storage and retrieval system and having a demagnetization field balance element for increasing a read sensitivity of a giant magnetoresistive spin valve read sensor.
Giant magnetoresistive (GMR) read sensors are used in magnetic storage systems to detect magnetically-encoded information stored on a magnetic medium or disc. A time-dependent magnetic field from a magnetic storage medium or disc directly modulates the resistivity of the GMR read sensor. The change in resistance of the GMR read sensor can be detected by passing a sense current through the GMR read sensor and measuring the voltage across the GMR read sensor. The resulting signal can be used to recover the encoded information from the magnetic storage medium or disc.
A typical GMR read sensor has a GMR spin valve that is a multi-layered device formed of a nonmagnetic spacer layer positioned between a ferromagnetic pinned layer and a ferromagnetic free layer. A magnetization of the pinned layer is fixed in a predetermined direction, typically normal to an air bearing surface of the GMR spin valve, while a magnetization of the free layer rotates freely in response to an external magnetic field. An antiferromagnetic material is typically exchange coupled to the pinned layer to fix the magnetization of the pinned layer in a predetermined direction.
Shields are generally placed on either side of the read sensor to ensure that the read sensor reads only that information which is stored directly beneath it on a magnetic medium or disc. Regular increases in areal densities of the magnetic media have made it necessary to regularly decrease the spacing between the shields positioned on either side of the read sensor. This decrease in the spacing between the shields has had the negative impact of decreasing the efficiency of the read sensor, thereby decreasing the read sensitivity of the read sensor, since the flux emanating from the magnetic media reaches a smaller portion of the read sensor.
This decrease in efficiency can be counteracted by decreasing the stripe height of the read sensor, that is, the length of the read sensor along its side perpendicular to the air bearing surface. However, decreasing the stripe height of the read sensor increases the demagnetization field acting upon the read sensor, thereby increasing the effective anisotropy of the read sensor, which in turn decreases the read sensitivity of the read sensor.
There is therefore a need to increase the read sensitivity of a read sensor of a magnetic read head by increasing the read sensor's efficiency without negatively impacting the effective anisotropy of the read sensor.